1. Field of the Invention
The invention relates to a converter for preparing steel, having a refractory lining including a wear lining of refractory bricks, the wear lining being provided at the bottom of the converter with a plurality of gas supply devices for supply of stirring gas to the molten bath in the converter. The invention also relates to the gas supply devices used in the wearing lining of such a converter. These gas supply devices are worn away with the wearing lining. The gas supply devices form scavenging points.
2. Description of the Prior Art
A converter as described above is known and used in practice. During the preparation of the steel in such a converter, oxygen is blown onto the bath by an oxygen lance from above, while a non-oxidising gas such as argon or nitrogen is also fed into the bath through the gas supply devices in the bottom of the converter. The purpose of this is to bring about an extra mixing of the bath, as a result of which metallurgical advantages are gained. It is therefore important that as far as possible, the gas supply devices remain operational during a campaign of the converter. At the end of a campaign, the wear lining is replaced.
For the gas supply devices so-called gas-permeable wall elements have been used, of a type such as for example is shown in EP-A-No.79655, in the name of the assignees of the present applicants. Gas-permeable wall elements of this type have a metal box structure in the shape of a lining brick, the bottom of which is connected to a gas supply. The box structure is fitted with a gas-permeable refractory lining. FIG. 1 of the accompanying drawings illustrate such a device.
One problem with this type of gas-permeable wall element is that its rate of wear, and that of the wear lining round about it, during a campaign is faster than the wear of the other parts of the wear lining in the bottom of the converter. Thus, the wear of the gas-permeable refractory lining of the gas-permeable wall element progresses ahead of the wear of the wear lining. In addition the wear lining near the gas-permeable wall elements is attacked faster than the wear lining at a greater distance from the gas-permeable wall elements.
Another problem with this type of gas-permeable wall element is that one or more of the elements becomes prematurely unusable during the campaign as a result of blockage because the steel from the converter penetrates against the gas flow into the gas-permeable channels of the gas-permeable wall element. Experience is that a wall element once blocked remains blocked upon further wear.
EP-A-No.155255 discloses a gas supply device of a panel shape formed by two metal plates which are joined together at opposite side edges by welding and are held apart by spacers located between them which form a number of parallel gas flow passages extending upwardly of the panel between the plates from a gas distribution box at the bottom of the panel. The panel is located between bricks of the wear lining with the distribution box in the permanent lining. The spacers are intended to prevent crushing of the plates together during heating up of the converter, but cannot prevent bulging apart of the plates by the pressure of the gas between the plates. Such bulging may enlarge the gap between the plates to allow molten steel to enter, leading to blockage of the gas supply device.
The panels of EP-A-No.155255 are located in transverse joints of the wear lining, i.e. joints transverse to the direction of the courses of bricks as seen in plan view. This means that the bricks adjacent the panel do not need to be modified to accommodate the panel, but also that the length of the panel in this transverse direction is limited to the transverse dimension of the course. This restricts the gas-flow capacity of each panel. To enable proper control of the gas flow through each panel, the panels have individual gas supply lines. All the supply lines must pass away from the converter via the pivoting trunnions of the converter. It is therefore of importance to minimise the number of gas supply devices.